1. Field of the Invention
The present invention relates generally to an improved resonating chamber and, in particular, to a sound attenuating system for use with drums and other acoustic articles.
2. Description of Prior Art
An instrument used for projecting, transmitting, and/or enhancing sound typically includes a solid body with a hollow cavity and a resonating element, such as a membrane, a string, or a diaphragm. For example, a drum can be made with an animal skin or synthetic film stretched over an open end of a hollow body. When a user strikes the resonating element, the vibration of the resonating element produces a sound that is characteristic of the instrument. Many factors can influence the sound produced. These factors include, for example, the types of materials used for the body and for the resonating element, the shape of the body, and the addition of other components. For example, a snare can be added to the membrane or the body of a drum to further enhance the sound. Typically, a user can tune the instrument by adjusting the tension applied to the resonating element. However, the tuning range is rather limited. Furthermore, the ability of the instrument body to project, transmit, and/or enhance sound is rather limited due to the destructive interference of sound waves carried by the instrument body. Accordingly, there is a need for improving the tunable range of the instrument and the ability of the instrument body to project, transmit, and/or enhance sound.
It is well established that different metals vibrate at different frequencies. Differences in various metals can be felt in the weight and flexibility, and heard from the differences in resonant frequency, harmonics, and dampening of the different tuning forks. Table I below shows various properties of a number of metals and other materials.
TABLE IDensityTradeEρLiquidusFrequencyName(GPa)(g/cm3)Temp. (° C.)Composition(Hz)Poly-2.01.2—C H—carbonatePure tin49.97.28232Sn 99.9%—Zn104.57.1420Zn 95%(d)Free8.50930-95060Cu-37Zn-129cutting3Pbbrass360Yellow100.6930-95070Cu-30Zn156 + 950brass(cartridge)Copper129.88.941,084Cu 99%190110CDA 954,550-640Cu-11Al-190 + 1,400Al-Bronze4Fe-(d)2.5maxNiZr 702986.511,855Zr-4.5maxHf200 + 1,250Brush1318.25880-950Cu-1.9Be206 + 1,400alloy 190Monel 4001858.831,30065Ni-30Cu-2331Mn-1.5FeAZ3144.71.78600-640Mg-3Al-1Zn255(d)Ti grade 21204.511,665Ti-max: 0.252.56 + 1,630O-0.3Fe-0.1C-0.03Ni-0.015HStainless1938.01,400-1,420Fe-18Cr-2603039Ni-2Mn-1Si-0.15C-0.6Mo-max:0.2P-0.15SInconel2088.441,290Ni-22Cr-260 + 1,4006259Mo-4Nb-0.3Ti-0.3Al6061-T668.92.70575-630Al-1.0Mg-260 + 1,6000.6Si-MnA6 tool2007.841,530Fe-2.2Mn-266steel1.2Mo-(hard)1.1Cr-0.7C1018 steel350-4907.91,500-1,530Fe-0.18C-267 + 1,6660.7MnA6 tool>200~7.841,450Fe-2.2Mn-276steel1.2Mo-(soft)1.1Cr-0.7CBy way of example, tuning forks made by the forgoing materials produce a distinctive ring. The dense copper alloys have a lower pitch, while the stiff steel alloys have a higher pitch. One can hear clear differences between brass, bronze, copper, and copper-beryllium. The free machining brass with 3% lead has the lowest pitch. It is known that steel and 6061 aluminum sound similar because steel's threefold increase in stiffness is compensated for by its threefold increase in density. The polycarbonate does not resonate at all, nor does the pure tin because it bends every time it is tapped to resonate. Magnesium, zinc, and aluminum-bronze dampen out within a few seconds. The Monel (Ni—Cu) and the Inconel (Ni—Cr) resonate loud and long. Hardened A6 tool steel resonates at a lower frequency than annealed A6 tool steel. Several metals, including zirconium, titanium, and Inconel, resonate with harmonics. There are almost 100 metallic elements, and when combined, the number of commercial alloys reaches the tens of thousands.
The tone of a tuning fork is a function of the dimensions, the density, and the elastic modulus of the metal from which it is machined. If the dimensions are kept the same, but the metal is changed, then a different frequency will result from the different densities and the elastic moduli.
                    f        =                  k          ⁢                                    E              ρ                                                          Equation        ⁢                                  ⁢        A            In Equation A, the resonant frequency f is related to the dimensions k, the elastic modulus E, and the density ρ. The density of a metal is a function of its crystal structure and atomic weight. The elastic modulus is a measure of the stiffness of the metal, that is, how tightly the atoms are bound. Metals with strong atomic bonding are not only stiff, but also have high melting points.
It is known to use sound attenuation or modulation for drums and other resonating devices, for example by muffling or altering the drum head tension or by altering the drum beater. However, there is a need for a device or system for adding pleasing frequencies to the sound of a drum or other resonating device when the drum is struck or vibrations are applied to the resonating device.